1. Field of the Invention
This invention relates to a laparoscopic instrument assembly having a removable tip, and in particular, having a removable tip provided with a double threaded design and an electrical return path.
2. Background of the Invention
Medical procedures such as laparoscopy and the like, which employ a tip at the end of a tube for insertion into the patient, are beneficial because the incisions necessary to perform them are minimal in size, therefore promoting more rapid recovery and lower costs. For example, a patient who undergoes laparoscopic surgery may typically return to normal activity within a period of a few days to about a week, in contrast to more invasive procedures requiring a relatively larger incision (which may require about a month for recovery). (Although the term “laparoscopic” is typically used hereinafter, such use of the term “laparoscopic” should be understood to encompass any such similar or related procedures such as, for example, arthroscopic, endoscopic, pelvoscopic and/or thoroscopic or the like, in which relatively small incisions are used.)
Current surgical devices are designed to function with mechanically operated tips. In other words, the design of a threaded tip and shaft assembly is specifically designed to mechanically attach a tip and also be able to transfer a force to the tip. Some existing laparoscopic devices use a screw-type threaded interface that does not provide low electrical resistances across the interface unless both the inner and outer thread forms are screwed together very tightly. However, it is difficult to build two or more coaxial thread forms that can be simultaneously mated and tightly fit together. Since tolerances and machining inaccuracies occur, one of the two threaded assemblies will always be tighter than the other, resulting in energy losses across the interface.
FIG. 1 shows a laparoscopic instrument assembly in accordance with the related art. Assembly 10 includes handle member 12 and shaft 14 operably interconnecting handle member 12 and removable tip 16. Removable tip 16 may be provided as part of assembly 10 or obtained separately. Distal end 22 of the shaft 14 is operably connected to tip 16 for actuation of surgical device 24 on tip 16.
FIG. 2 shows a shaft a body of a laparoscopic assembly in accordance with the related art. Sheath 18 is held in conventional manner within casing 26 using collet 44. Additional securing mechanisms, such as a detent, are provided to ensure that sheath 18 is tightly secured within the body. When collet closer 28 is tightened about collet 44, detent member 52 is forced inwardly by the internal surface of collet closer conical portion 46, partially enters collet axial bore 50, and engages sheath groove 40 to hold sheath 18 firmly within the body. The number of detent members 52 and bores 54 is selected to optimize the gripping power of the detent members on sheath 18. At least one radial bore 68 is also formed in rod 32 to extend from the outer surface of rod 32 into and open to axial bore 66. Each radial bore 68 contains a detent member 70 therein for mating engagement of detent member 70 with groove 58. The number of detent members 70 is selected to optimize the gripping power of the detent members on rod 20. Each detent member 70 engages groove 58 during actuation of surgical tip device, preventing removal of rod 20 from axial bore 66. However, sheath 18 may be released from casing 26 as described above, and detent members 70 may be disengaged from groove 58.
FIG. 3 shows an instrument tip and actuator assembly in accordance with the related art. At the rear of the casing structure 24, a yoke 26 is located having an external thread 25 formed on the rear end thereof. In addition to the continuous thread 25 formed on the yoke 26, the operable tip 14 is provided with a continuous internal thread (not shown) formed on the inner surface of the tip casing structure 24. The actuator 12 includes an outer sheath 36, having an insert which may be press fit into the sheath 36, with a continuous external thread 39 formed at its forward end, the thread 39 being of matching pitch and diameter to the internal thread provided on the operable tip 14. The thread 25 is configured to threadedly mate with internal threading of an actuation rod (not shown) slidably positioned within the sheath 36 such that sliding movement of the actuation rod operates the tip.
FIG. 4 shows an exemplary embodiment of a cutting and sealing device of a laparoscopic instrument assembly in accordance with the related art. US Publication No. 2009/0198224, the entire contents of which are hereby incorporated by reference, discloses a tissue cutting and sealing device provided on the distal end of an endoscopic device 10. A pair of opposing jaws 20 and 40 dimensioned to grasp tissue therebetween is also provided, and a heating assembly 22 is provided on jaw 20. Heating assembly 22 includes a ceramic body 24 with a metalized portion 26 extending along a top surface of ceramic body 24. The heater assembly 22 provides a resistive heating element 26 on top and integral with the ceramic substrate 24. The design is advantageous since the temperatures in ceramic body 24 are always lower than the temperatures in the metalized portion 26. In addition, the ceramic acts as a heat spreader that increases the effective seal area of the heater. The design promotes tissue sealing adjacent to the ceramic and tissue cutting adjacent to the metalized portion.